Unfortunately, there is no way to stop "clubs" from forming that will upvote each other. In fact, the use of categories to filter which posts you want to look at could be considered a form of club. For example, I love dogs, all dogs, so I tend to look at post made in the dogs category and upvote as many of them as I can.

Since Steemit is fairly young, there really aren't that many people in here yet. As the numbers grow, you will see better results with more votes being spread around to more people. Eventually, I think we will also see bots developed that will target and down posts that are exclusively for "clubs". Just as we are seeing the first bots that target potential plagiarized content.

There will always be a small group of whales who can set a post on fire and the followers that will jump on any post upvoted by whales, but that is the nature of the game. And is what keeps a lot of us posting, hoping for a big hit.